This invention relates to an apparatus for the assembly of radial tire components, and more particularly, to a building drum for the assembly of a belt-tread stock package for subsequent use in the final two-stage assembly step of a radial tire, at which operation the belt-tread stock package is attached to and consolidated with a carcass which is previously assembled on a first stage assembly machine.
When applying the two-stage method of assembling a modern radial tire, it is common to use a first stage carcass assembly machine and a second stage machine on which the carcass from the first stage is chucked by its beads and then transformed from a cylinder into a toroidal shape, at which time the belt-tread stock package is added to the carcass, and the assembly is then consolidated by stitching the two tacky subassemblies together.
The basic elements of a modern radial ply pneumatic tire for automobile and light truck use consist of an inner liner, one or more plies, sidewalls, beads, fillers and other bead reinforcements, all of which, when properly assembled, form a subassembly called a first stage carcass, as well as a belt-tread stock subassembly comprising one or more belts incorporating steel cord or other suitable cord materials and a length of tread stock combined to form a belt-tread stock package. The first stage carcass and the belt-tread stock package are then combined into a green tire, which is subsequently molded and cured in a vulcanizer.
A form of apparatus for building and combining the two assemblies is described in U.S. Pat. No. 4,402,782 issued Sept. 6, 1983 to the assignee of this application, includes a machine for building a first stage carcass, a second machine for building a separate and distinct second stage radial tire belt-tread stock package, a means to convey the belt-tread stock package into circumferential coaxial contact with the shaped carcass, and stitching means for consolidating the two assemblies into a green tire.
In particular, FIGS. 2 through 6 of that US patent show a form of building drum for use in assembling the belts and tread stock, such drum having a plurality of drum segments with arcuate outer shoe members which cooperate to form the building surface of the drum. Those segments are supported, and radially adjusted, through a set of links, connecting pins, and a pair of axially adjustable spider members. The spider members are moved toward and away from each other by pneumatic cylinders, and a rack and pinion mechanism connects the two spider members to coordinate their motion. While this construction has been effective, it is not suited for incorporation into an automated tire assembly system due to its design concept. Furthermore, the shoe members, having straight sides which extend parallel to the central shaft of the drum mechanism, will present wider gaps between them as the drum mechanism is expanded to handle larger diameter belt/tread stock packages.
Consequently, in an attempt to automate certain tire assembly operations it was noted that there was a need for a building drum that is programmable, remotely adjustable, which requires relatively few parts, is simple in design, accurate when being set to specific building diameters, and inexpensive to manufacture and maintain. In addition, there has been a need to increase the building diameter range of the various drum sections minimizing the gaps between the drum segments, such that essentially continuous support is being provided for the belt components, in particular, as they are being placed and assembled on the drum surface.